1. Field of the Invention
This invention concerns a device for marking successive stakes so as to establish a horizontal baseline for elongated masonry structures, and more particularly relates to the production of masonry walls by the stacking of uniform construction units.
2. Description of the Prior Art
The accurate positioning of two distantly separated points within the same horizontal plane has long been a primary consideration of surveying techniques. The use of laser beam level devices has facilitated easier and more accurate surveying applications.
In the construction of elongated masonry structures such as building foundations and cross terrain walls, it is important to establish a level foundation consisting of a first row of building blocks positioned upon a stable footing such as poured concrete. The production of a level foundation and subsequent wall structure is usually accomplished by driving metal stakes, known as grade stakes, into the ground in a sequence along the desired path of the wall, and causing a taut string to engage the stakes at a proper elevation for guiding the pouring of concrete or placement of masonry building units
In order to establish the proper elevation of the level string, each stake has to be marked so as to accurately indicate the site of string wrapping or tying. Such marking of grade stakes has been accomplished by surveying techniques. In one such technique, a laser level transmitter is employed in conjunction with a receiver, called a xe2x80x9crod-eye,xe2x80x9d which is attached to a long stick that can be hand-held in vertical position. The lower extremity of the stick is held against the grade stake, and a mark is made on the grade stake when the rod-eye indicates by an audible or visual signal that it is on the same horizontal plane as the laser transmitter unit.
The stick employed in such marking technique is usually of six foot height and 1xe2x80x3xc3x972xe2x80x3 cross section, and the rod-eye is attached to the top of the stick. Workers have found it difficult to stabilize the lower extremity of the stick along the grade stake for marking because of the top heavy nature of the stick with rod-eye. Such manipulation is particularly difficult when the grade stake is not vertical.
In instances where an outdoor wall runs across terrain that is not level, it is generally necessary to create a stepped wall wherein the foundations of successive segments of the linear extent of the wall are at different elevations, but still horizontally disposed. The difference in elevation between such successive segments is generally caused to be equal to the height of one or more construction units employed in making the wall. For example, in a masonry wall constructed of building blocks of 8xe2x80x3 height, an elevational difference of 8xe2x80x3 between contiguous wall segments would cause all the blocks to maintain a horizontal disposition in straight lines. No simple provision has heretofor been disclosed for enabling a rod-eye affixed to the stick to easily and accurately adjust to the different elevations required in successive stepped segments of a wall on non-level terrain.
It is accordingly an object of the present invention to provide apparatus for use with laser leveling techniques for marking grade stakes so as to facilitate formation of a level string line to establish a horizontal foundation for a masonry wall.
It is another object of this invention to provide apparatus as in the foregoing object particularly well suited for use in masonry walls employing blocks of uniform height.
It is a further object of the present invention to provide apparatus of the aforesaid nature which is easily adjustable for producing a stepped wall.
It is yet another object of this invention to provide apparatus of the aforesaid nature compatible with grade stakes that are not vertical.
It is a still further object of the present invention to provide apparatus of the aforesaid nature of simple, durable construction amenable to low cost manufacture.
These objects and other objects and advantages of the invention will be apparent from the following description.
The above and other beneficial objects and advantages are accomplished in accordance with the present invention by an apparatus for marking grade stakes driven into the ground and having an upper extremity, said marking being for the purpose of facilitating formation of a level string line to establish a horizontal foundation for the construction of a masonry wall, said apparatus comprising:
a) stake engaging means securable upon a stake and having retaining means to slidably accommodate and secure a vertically moveable member,
b) a straight positioning rod elongated between top and bottom extremities defining the length thereof, and having a uniform rectangular cross-sectional configuration with consequently formed four elongated flat surfaces oriented as front and rear surfaces, outer side surface and stake-directed side surface,
c) track means in lengthwise association with said stake-directed side surface and interactive with said retaining means to permit vertical sliding movement of said positioning rod,
d) a story rod slidably secured by said front surface and containing a scale of linear measurement indicia which facilitates repeat measurements of constant length,
e) a rod-eye mounted upon said story rod and adapted to receive a leveling beam from a distantly located laser transmitter and produce a visual and/or audible signal in response to receipt of said leveling beam, said signal dictating the elevational distance of said positioning rod above said horizontal foundation, and
f) marking guide means associated with the bottom extremity of said positioning rod to facilitate placement of a mark upon said grade stake representing the location for tying a level string that tautly extends between sequentially contiguous stakes.